SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a78ba3effcd8fd2121b0840b8afd59e86aee2612f7099c96e5ffdbdd02f67a41' 
  AND token = 'WhfToTIYMS0tZ1aGojKPY6XNn5WXU9POjyPig4pdmrg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}